Since their recent discover and because of their unique structures and peculiar chemical-physical properties, carbon nanotubes, fullerene and their derivatives have been object of many studies and researches that demonstrated their profitable and innovative applications in many fields.
The main applications of these new nanomaterials could be: realization of structural materials with unique mechanical characteristics; production of nano-metric devices (nano-motor, nano-transistor, etc.); as additive for polymers; production of Field Emission Device, (flat panels for high resolution electronic displays); as “vehicles” for pharmaceutically active molecules; as hydrogen storage media to be used in fuel cells technology.
Nevertheless, nowadays many of these applications remain at the stage of preliminary studies or prototypes due to the lack of sufficient quantity of raw materials (nanotubes, fullerene and their derivative) having costs compatible for the development of these applications on an industrial scale. Furthermore, really the lack or the excessive cost of these materials represent a further obstacle to the research for other new applications.
During the last years, multi wall nanotubes (MWNT) or single wall nanotubes (SWNT), fullerene and their derivatives were and are produced utilizing several methods, among those the most important surely are that ones that have been demonstrated, really or in perspective, to be able to supply large amount of product at limited costs.
All the methods used until now may be divided in two categories, depending on the characteristics of the precursory material utilized.
The first category includes all the methods where the precursory material is constituted by a solid carbon-based material (graphite rods or carbon powder); the second category includes all the methods where the precursory material are in liquid or gas phase.
For all the methods pertaining to the first category, it is necessary to reach high temperatures (>3600 K) to vaporize the precursory material, which may be achieved in various ways. In the case of solid precursory material, as graphite rod, the main methods used may be resume as follow:    vaporization by arc discharge;    vaporization by laser ablation;    vaporization by concentration of solar energy;    vaporization by induction heating;    vaporization by direct current flow;    vaporization by sputtering;    vaporization by electronic beam bombardment.
The method of vaporization by inductive coupled plasma is used only in the case where the solid precursory material is constituted by carbon powders.
In the second category, i.e. comprehensive all the methods based on the decomposition of a precursory material (containing carbon) in liquid or gas phase (hydrocarbon, alcohol, ferrocene, etc.) it is possible to arrange the following ones:    methods of thermal decomposition of a precursory material in gas or vapour phase in presence of catalysts at low temperature (450–800° C.), or at high temperature (800–1200° C.), inside a chemical vapor deposition (CVD) reactor;    method for chemical vapor deposition enhanced by radio frequency plasma (PE-CVD);    method for chemical vapor deposition enhanced by microwave plasma (MP-CVD);    method named HIPco, i.e. a process in gas phase at high pressure with carbon monoxide as precursory material;    flame combustion method.
In spite of the many production methods above mentioned, only some of them are currently used for productions of considerable amounts for commercial purpose as well.
Therefore, at the present time, the prevalent production methods suitable for an effective commercialization of nanotubes, fullerene and their derivatives, are those listed as follow.
Pertaining to the first category, i.e. the methods that use solid precursory material, the arc discharge method is up to day the most common and spread, due to its intrinsic simplicity and to its low cost for the assembly of a production device.
By means of this method it is possible to produce nanotubes, fullerene and their derivatives. Thanks to this method, mainly devoted to research aims, many small enterprises arose for producing and commercializing: nanotubes SWNT (quite small with diameters from 0.6 to about 2 nm) and nanotubes MWNT (small with internal diameters from 0.6÷3 nm to about 20 nm of external diameter), fullerene and their derivatives.
The nanotubes produced in this manner are generally of good quality, with few structural defects and the MWNT are produced without the aid of catalysts.
Nevertheless, the arc discharge method presents two heavy limiting factors from the productivity point of view: i) it is not a continuous production method; ii) it is not a scalable method; in fact, with discharge currents over around 150A the production yield of the device decrease quickly, since the plasma jet speed becomes too high and, consequently, the time of permanence for the carbon clusters in the high temperature plasma is too short.
It is still possible to realize considerable productions by this method, not increasing the electric power of a single device, but arranging multiple devices in battery. In any case, the amount of solid material that it is possible to vaporize in a optimized device results generally less than 10 gr./h.
Pertaining to the methods classified in the second category, those starting from liquid or gas phase precursory material, and for the production of fullerene only, the method of low pressure flame combustion (method used by the companies Frontier Carbon Corporation—JP and Nano-C—USA) prevails over all the competitors for both productivity and yield. The CVD methods produce mostly MWNT with considerable dimensions (external diameters more than tens nano-meter).
Even if it has not yet begun the commercialization of products, Toray company—JP declared the development a new method based on catalytic decomposition of hydrocarbons on dispersed metallic particles in zeolytes for the synthesis of DWNT with external diameters between 1 and 3 nm.
The HIPco method is until now the only one (besides arc discharge method) able to produce SWNT in considerable quantity for selling, as well as research aims.
CNRI-Mitsui company—JP has recently announced a new CVD process for the production of SWNT named Alcohol Catalytic Chemical Vapour Deposition.
However, on the basis of which above described, it is clear that a new system for producing nanotubes, fullerene and their derivatives-flexible, able to be set up in a simple way only by changing the precursory material and the process parameters, with low plant and running costs, with a continuous automated production, with production yield largely higher than those possible with arc-discharge method, is of great interest. Such a new production system could be surely attractive for all that would autonomously produce many carbon-based nano-materials. By this innovative method it would be possible to realize little, distributed plants with costs truly competitive in respect to plants, e.g. as required for CVD methods, committed to production of a specific product and requiring very large scale industrial structures and considerable investments for their realization.